X-ray film package with water soluble separator and water soluble light opaque envelope



March 19, 1968 E. L. SACHS 3,374,352

X-RAY FILM PACKAGE WITH WATER SOLUBLE SEPARATOR AND WATER SOLUBLE LIGHT OPAQUE ENVELOPE Filed Nov. 2, 1966 E/mu L. Sachs By Dav/s, Hoxl, Fa/fh/ul/fi Hapgood Af/omeys United States Patent ABSTRACT OF THE DISCLOSURE An X-ray film package having an X-ray sensitive sheet enveloped by a light-opaque, radiolucent, water soluble plastic film and a radiolucent, water soluble separator between the emulsion of the X-ray sensitive sheet and the envelope to prevent adherence of the envelope to the emul sion.

This application is a continuation-in-part of my prior, co-pending application Ser. No. 424,728, filed Jan. 11, 1965, now abandoned.

This invention relates to an X-ray film package which may be processed automatically in a conventional lighttight developing machine without the need of a darkroom during preparation of the film while it is being readied for the machine. More particularly, this invention relates to an X-ray film package wherein the photographic emulsion is covered with and protected by a radiolucent, lightopaque, water-soluble envelope.

Emulsions on X-ray film in common use today are sensitive both to visible light and to radiation in the X-ray portion of the electromagnetic spectrum. Therefore, it is necessary to provide such film with a covering or coating which is opaque to ordinary light, but radiolucent to X-rays. Ordinarily, the X-ray film package in present use comprises a sheet of appropriate photographic film and a backing sheet of lead foil, both of which are enclosed in a light-tight, light-opaque paper wrapper. After exposure, this film package is taken into a darkroom where the protective, light-opaque paper covering is removed and the film is subjected to the usual developing processes. It is desirable to eliminate the need for a darkroom where X-ray films are exposed, developed and observed, such as in dentists and physicians offices. Furthermore, with the growth of in situ X-ray examination of structures such as oil wells, ship hulls, solid propellant grains for rockets, etc., it is desirable to be able to develop the X- ray films on location where darkrooms are not available.

Attempts in the prior art to solve this problem are exemplified by United States Patent No. 3,152,252 wherein an envelope of a water-soluble material was substituted for the above mentioned paper enclosure. In one form of the X-ray film package of that patent, sheets of black paper are placed on either side of the film inside the water-soluble enclosure, to prevent fogging of the film by light. That package has various attendant deficiencies, among them being light leakage along the edges of the sheets of black paper and the consequent fogging of the X-ray film, the tendency of the sheets of black paper to adhere to the X- ray film during the developing process causing uneven and improper development, and the accumulation of paper sheets in the processing tank necessitating frequent removal of the paper to avoid clogging the fluid outlets. Furthermore, if a drain becomes clogged during the processing of a film, the tank becomes inoperative for further processing and must be opened in a darkroom to permit removal of the paper.

In another form of the prior art X-ray film package,

the black paper sheets are replaced by a coating of lamp black or silver nitrate on the inside surface of a water soluble envelope that is directly adjacent to and in surface contact with the X-ray film emulsion.

When that film package was processed by immersion in the water bath, the gelatin of the X-ray film apparently became impregnated with amounts of the dissolving envelope material. Particles of its envelope material firmly adhered to the X-ray film and could not be removed even by rubbing. Since the processing solutions could not reach the areas of the film surface under the particles, undeveloped spots remained on the X-ray film at the end of processing. The silver nitrate coating in creased the radiopacity of the package making it necessary to increase radiation exposure of the subject and rendering faint traces such as hairline cracks unobservable.

Accordingly, it is one object of this inveniton to provide a novel X-ray film package which will facilitate the development thereof without the need of utilizing a dark-. room.

It is another object of this invention to provide an enclosure for an X-ray film package which prevents visible light from reaching any portion of the light-sensitive film and which does not tend to obstruct the fluid outlets of, nor accumulate in, the processing tank.

It is a further object of this invention to provide an enclosure for an X-ray film package which will be removed reliably and completely by a water bath and which will not adversely affect the quality of the developed picture,

Further objects of the present invention are to provide an X-ray film package that, during processing, leaves no residue either on the X-ray film itself or in the processing tank and to provide a light-opaque enclosure for an X- ray film that does not necessitate an increased X-ray exposure nor reduce the clarity of the finished X-ray plate.

The present invention, in one form, provides an X-ray film package including a conventional base sheet with a light sensitive emulsion on at least one surface thereof and having an envelope of light-opaque, radiolucent, water-soluble plastic film material and a separator layer between the envelope and the photographic emulsion. The separator layer may, for example, be a conventional tissue paper having a relatively small amount of binder in relation to the paper pulp whereby the tissue paper disintegrates rapidly when agitated in water. The envelope material may be for example, polyethylene oxide. Such material is radiolucent and is made opaque to visible light by providing a light-opaque coating on the inner or outer, or both, surfaces thereof, or by including a lightopaque pigment in the material itself. Suitable opacity can be obtained by inking the inner surface of the envelope with an organic based red marking ink, and the outer surface with an organic based black marking ink. Such a coating will not reduce the radiolucency of the envelope 1 and will not leave any residue in the water bath.

This X-ray film package can be processed without resort to the use of a darkroom by placing the package in a light-tight unit, for example, a unit of the type described in United States Patent No. 2,621,571. In this apparatus, the film package would first be subjected to a water bath in order to dissolve the plastic envelope and separator layer. The water is then flushed from the developing tank, carrying with it the dissolved material. The photographic film is then subjected to the usual developing operations, such as are described in United States Patent No. 2,621,571.

Preferably, for dental X-ray utilization of my invention, the plastic covering layer comprises a plastic material having a water softening point slightly above the temperatures likely to be encountered in the human mouth, 106 F., in order to avoid premature dissolution of any portion of the envelope. and the consequent exposure to light of the emulsion. A plastic film comprised of polyvinyl alcohol may have a water softening temperature in the range of 140180 F., depending upon the isotacticity of the material. Of course there would have to be used an X-ray film having a hardened emulsion to withstand the temperature of the initial hot water bath.

Alternatively, the covering layer may be comprised of a polyethylene oxide or a polyvinyl alcohol or having a softening point below the temperatures normally encountered in the human mouth. In such cases, however, the above described X-ray film package would be enclosed in a water tight, water proof envelope. After X-ray exposure and removal from the human mouth, the package would have the water-proof envelope removed therefrom and would then be placed, as described above, into the light-tight processing unit. However, since the water softening temperature would be considerably lower, for example, 4080 F. for a film of polyethylene oxide, the temperature of the water in the initial dissolving bath could be reduced. This would permit the utilization of X-ray films having the standard emulsions.

Other objects and attendant advantages will be apparent from the following description taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a sectional view of an X-ray film package formed in accordance with one embodiment of the present invention;

FIGURE 2 is a schematic representation of apparatus for manufacturing an X-ray film package embodying the present invention; and

FIGURE 3 is a sectional view of an X-ray film package showing a second embodiment of the present invention.

Referring now to FIGURE 1, there is shown, in 5635- section, an X-ray film package 8 including a conventional X-ray film 9 of well-known construction having a base or support 10 on at least one surface of which is coated a light or photo sensitive emulsion 11. The film 9 has juxtaposed thereon separator layers 12, for example, sheets of tissue paper having a binder which permits rapid and complete dissolution of the paper when immersed in a water bath. A protective envelope 13 comprised of a water-soluble plastic material, for example, polyethylene oxide or polyvinyl alcohol encloses the separator layers 12, base 10 and emulsion 11. The envelope 13 is formed of a pair of plastic sheets 14 which are sealed along their edges 15, by any conventional suitable means, such as heat-sealing apparatus.

The envelope 13 is rendered opaque to visible light by an appropriate light-opaque surface coating or by the inclusion in the envelope material of an appropriate pigment. A light-opaque coating preferably is provided on the envelopes inner surfaces 16 that are in face-to-face contact with the separator layers 12. Alternatively, the coating may be placed on the envelopes outer surfaces 17, but there is the attendant risk of surface scratching the coating which would permit the entrance of light to the light sensitive emulsion 11. A further method for rendering the envelope 13 light opaque is to coat the inner surface 16 of the envelope 13 with a red marking ink and the outer surface 17 with a black marking ink. The black surface greatly reduces the intensity of light penetrating it and the inner red surface allows only red light to pass through which will not fog the X-ray film. It is important that the inks have an organic base since an aqueous base will attack the water soluble envelope. As still a further alternative, appropriate pigments may be admixed with the plastic material from which plastic sheets 14 are made, whereby the sheets 14 are rendered integrally opaque to visible light.

It is desirable that an X-ray film package for dental use have a lead foil backing sheet 18 in order to reduce the intensity of X-rays striking tissue beyond the film package and to reduce secondary or backscattered radiation which might affect the image on emulsion 11. The lead foil backing sheet 18 is detachably fastened, for example, by rubber cement or glue, along portions of its periphery on the outside of one of the plastic sheets 14.

The X-ray film package 8 illustrated in FIGURE 1 is adapted to be placed in the human mouth for dental X-ray exposure of the emulsion 11. Accordingly, the plastic envelope 13 is formed of a material, described below, which does not dissolve in saliva at the temperatures likely to be encountered in the patients mouth, 95l06 F. After being exposed to X-rays, the film package 8 is removed from the patients mouth, the backing sheet 18 is detached, and the package is then developed. The package 8 is processed without resort to the use of a darkroom by placing the package in a lighttight processing unit, for example of the type disclosed in United States Patent No. 2,621,571, as described above. An alternative apparatus and processing method are described in United States Patents Nos. 2,989,911 and 3,000,288.

The envelope 13 preferably is made of a suitable polyethylene oxide plastic sheet such as is manufactured by the Union Carbide Company under the tradename Radel WFAA-4050. This sheet has a nominal thickness of 2.0 mils, a tensile strength of 5000-l4,000 pounds per square inch and a 200% elongation. At 40 C., a 2 inch by 3 inch pocket will release its contents in one second and will completely dissolve in one minute. The heat sealing temperature range is 145-200 F. However, at these temperatures the sheet has a tendency to adhere to the heated sealing jaws, impairing the quality of the seal. I have found that the interposition of common waxed paper between the jaws and the plastic sheet eliminates this problem.

A water soluble, polyvinyl alcohol plastic sheet is available for use as the envelope 13 from the Reynolds Metals Co. under the tradename Renolon PVA/WS-75X. This film has a nominal thickness of 1.5 mils, a tensile strength of 4500-8500 pounds per square inch and a 300600% elongation. The sheet, preconditioned at 40% relative humidity and 75 F. for 2 hours, will produce a high quality heat seal with a sealing temperature of 340 F. and a pressure of 30 pounds per square inch gauge, and at a dwell time of /2 second. The sheet has an agitated rupture time of 15-35 seconds at F.; l0 20 seconds at F. There is a maximum of 0.1% residue at 90 F. for a 3 minute water exposure; a 0.1% residue at 140 F. for a 2 minute water exposure.

The water soluble separator layers 12 prevent spotting of the X-ray film during processing by acting as a barrier between the plastic sheets 14 and the X-ray film 9 itself. At the same time the separator layers facilitate dissolution of the plastic sheets 14 by physically separating them from surface contact with the adjacent X-ray film thus providing greater water-sheet surface contact.

The separator layers 12 have been described as being formed of weak, easily dissolving tissue paper; however, any dissolvable layer which does not adhere to or adversely affect the emulsion 11 can be used. For example, a film of wax upon the inner surface of the water soluble envelope 13 can also be employed.

One method of manufacturing the X-ray film package 8 is schematically illustrated in FIGURE 2. A first tissue paper sheet 12a and an integrally opaque first plastic sheet 14a are continuously fed from roll sources 19 and 20, respectively, pass over an idler roller 21 and onto a support bed 22. Sheets 12a and 13a then pass under a hopper 23 in which there is stored a supply of pre-cut X-ray films 9. The hopper 23 is equipped with a conventional timed release means 24 whereby individual X-ray films 9 are deposited at predetermined, spaced intervals on the paper sheet 12a. A second tissue paper sheet 12b and a second integrally opaque plastic sheet 1411, from roll sources 25 and 26, respectively, pass under rollers 27 and 28 Where they are juxtaposed to the upper surface of the films 9. Oscillating heat sealing jaws 29 fuse the edges of the plastic sheets 14 to form the protective envelope 13. In cooperation therewith, cutter 30 severs the interconnected =packages into individual X-ray film packages 8. Either prior to or after the cutting operation, lead foil backing sheets 18 are detachably fastened to the plastic sheet 14a.

A second embodiment of this invention is illustrated in FIGURE 3. An X-ray film package 32 comprises the film package 8 of the first embodiment wherein the protective envelope 14 is formed of a material which has a dissolution temperature equal to or less than the temperature encountered by the package 8 during use; for example, in the human mouth. In order to prevent premature dissolution of the envelope 14, Which otherwise would result in exposure of the emulsion 11 to light, a watertight, waterproof, tear resistant envelope 34 is provided. One suitable material for the water proof envelope is polyethylene. The envelope 34 comprises two parts, a primary body portion 35 which envelopes all but one side of the film package 8 and a water-proof tape 36 which closes the one open side and, in conjunction with the body portion 35, forms the Water-tight envelope 34. To facilitate removal of the envelope 34, a cotton string 37 is embedded in the tape 36 which, when pulled, opens the envelope 34. FIGURE 3 illustrates the primary body portion 35 being formed with a bite-wing tab 38 which provides a surface on which the patient bites to hold the film package 32 in place when taking certain views. The lead 9 foil backing sheet 18 is located either inside the waterproof envelope as shown, or on the outside surface thereof (not shown) and is removed when the waterproof envelope 34 is removed. After X-ray exposure of the film package 32, the envelope 34 and lead sheet 18 are removed and the remaining package is developed as described above.

Although the invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example, and other combinations and arrangements of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

What is claimed is:

1. An X-ray film package including a base, an X-ray and light sensitive emulsion on at least one surface of said base, a separator means contiguous to and co-extensive with said emulsion, said separator means being radiolucent and dissoluble and separable from said emulsion in water, and a protective envelope of radiolucent, lightopaque, water soluble, material enclosing said base, emulsion and separator means, said separator means isolating said envelope from said emulsion, submersion of said film package in water effecting dissolution of said envelope and said separator means.

2. A film package as defined in claim 1 wherein the protective envelope is polyethylene oxide.

3. A film package as defined in claim 1 wherein said separator means is a paper having a binder which permits rapid dissolution of said paper when immersed in water.

4. A film package as defined in claim 3 wherein the protective envelope is polyethylene oxide.

'5. An X-ray film package including (a) abase sheet,

(b) an X-ray and light sensitive emulsion on at least one surface of said sheet,

(c) a separator layer enclosing said sheet and emulsion, said separator layer being radiolucent and dissoluble and separable from said emulsion when in water,

(d) a protective envelope of radiolucent, light opaque, water soluble material, enclosing said sheet, said emulsion and said separator layer, said separator layer isolating said envelope from said emulsion, and

(e) an outer Water-proof envelope enveloping elements (a) through (d).

6. A film package as defined in claim 5 including means attached to said waterproof envelope for opening said waterproof envelope.

7. A film package as defined in claim 5 including a lead foil backing sheet on the side of said package remote from said emulsion.

8. A film package as defined in claim 7 wherein said backing sheet is between said protective envelope and said outer envelope.

9. A film package as defined in claim 5 wherein said outer envelope is polyethylene.

10. A film package as defined in claim 5 wherein said separator layer is a paper having a binder which permits rapid dissolution of said paper when immersed in water.

11. A film package as defined in claim 10 wherein the protective envelope is polyethylene oxide.

References Cited UNITED STATES PATENTS 3,037,117 5/1962 Telson 250-68 3,152,252 10/ 1964 Wainwright et a1 250-68 FOREIGN PATENTS 803,926 11/ 1958 Great Britain.

WILLIAM F. LINDQUIST, Primary Examiner. RALPH G. NILSON, Examiner. 

